Conventional liquid crystal displays (LCDs) include a substrate with a transparent cover connected thereto and disposed thereover. A cavity is formed between the substrate and the transparent cover, and the cavity is filled with liquid crystal. Optical properties of the liquid crystal change as an electric field that is applied across the liquid crystal changes. Therefore, by controlling the electric field appearing across portions of the liquid crystal, the optical properties of the liquid crystal can be changed in order to display information in the form of characters or numbers, for example.
However, many prior art techniques of manufacturing a liquid crystal display individually connect the transparent cover to each substrate. Therefore, production of many substrates in parallel, at the wafer-scale, of liquid crystal displays is hindered. Furthermore, application of a separate transparent cover is subject to error in the thickness uniformity of the liquid crystal material, deriving from imperfect flatness or parallelism of the substrate and cover. Therefore, the process of individually connecting a transparent cover oftentimes requires precise tolerances, which can be difficult to obtain.
Furthermore, in creating conventional liquid crystal displays, as well as many other types of microfabricated devices, a sacrificial layer is oftentimes deposited and then later removed through conventional microfabrication techniques, such as etching. The deposition and later removal of the sacrificial layer enables cavities or other hollow areas to be formed during the manufacturing process.
One prior art method for forming hollow areas within microfabricated devices includes the step of forming a porous material to encapsulate sacrificial material. The porous material includes many thousands of tiny holes that allow gases to pass through the porous material. Oxygen or an oxygen-plasma is allowed to move through the porous material, thereby vaporizing the sacrificial layer when the device is exposed to high temperatures (e.g., greater than 100 degrees Celsius). The gaseous sacrificial material egresses through the pores of the porous material leaving a hollow area where the sacrificial material once resided. The opening is usually plugged during a subsequent deposition step in order to seal the microfabricated device.
However, this type of technique for removing a sacrificial layer through a porous material requires the extra steps of exposing the device to oxygen plasma. The exposure of the device to oxygen-plasma can be potentially damaging to other elements of the device. Furthermore, the process of forming a suitable porous material can be difficult, since thousands of tiny holes need to be formed in order to develop a porosity sufficient for allowing sacrificial material to escape. Furthermore, as the porosity of the material is increased, the mechanical stability of the material is typically decreased. Therefore, manufacturing a sufficiently porous material that can withstand the high pressures associated with dissipating sacrificial material can be very difficult and costly.
Due to many difficulties, including the difficulties of forming cavities for liquid crystal displays, prior art techniques of manufacturing liquid crystal displays are inefficient and do not usually integrate liquid crystal displays onto a single substrate where mechanical components, such as the covers mentioned hereinbefore, are not separately attached. Thus, a heretofore unaddressed need exists in the industry for providing a system and method to efficiently microfabricate a fully integrated liquid crystal display.